Seismic exploration is practiced by utilizing data to determine location of subsurface strata. After wells are drilled in an area, logs of the earth formations can be used to locate and correlate the depth of various similar strata with respect to the wells. The logs also provide porosity data as well as production data. However, there are many unknowns and analysis of well data may not correlate in predicting reservoir production. For example, the same strata may be non-productive at one location and productive at another location. This can be due to a number of factors including depletion of the hydrocarbons by migration between different levels, faults which interrupt continuity of strata and a host of other reasons. By means of the present invention the predictability of reservoir production from a stratum is greatly enhanced.